The Epidemiology Branch (DESPR) is conducting a number of studies in collaboration with the Health Research Board and Trinity College, Ireland. These investigations are designed to determine the biochemical mechanisms by which folate reduces the risk for neural tube defects. Data and blood samples have been collected on a large proportion of Irish women delivering babies in Dublin. Samples from women whose pregnancy ended in the delivery of a child with a neural tube defect and control women whose pregnancy ended in the delivery of a normal child are being studied. Various aspects of folate metabolism and other nutritional measures are being examined. Ancillary studies are also being performed to determine whether other micro nutrients are involved in the pathogenesis of neural tube defects and how the risk for having an affected child varies from pregnancy to pregnancy in the same women.